1. Field of the Invention
This invention relates to a single piece plastic closure with a snap hinge having two parts connected by at least one hinge, and a flexible element generating the snap action, which is hingedly connected to the two parts of the closure.
2. Description of Prior Art
Plastic snap hinges for closures can be roughly classified into two types, namely those where the snap effect is generated by a tension element and those where it is generated by an elastically flexible element. This invention relates to a closure with a plastic snap hinge of the second type.
Conventional elastically flexible elements have a shape in the form of a letter "U" or "L", as, for example, is known from U.S. Pat. No. 4,911,324 or U.S. Pat. No. 2,630,239. The size of the elements is essentially determined by the spring path and the desired spring force. However, particularly in connection with the use of plastic tops, other marginal conditions which greatly affect the geometry of a plastic snap hinge are opposed to this. Conventional flexible elements cannot be used, particularly when employing tops with relatively large pouring spouts and a relatively flat lid. In the case of an L-shaped flexible element, the leg extending through the cover of the lid cannot be made sufficiently long, because otherwise it would extend into the sealing area of the pouring spout. A U-shaped flexible element cannot be made sufficiently large, because the low height of the lid does not provide enough space to accept the flexible element.
Another solution is taught by U.S. Pat. No. 3,629,901 where the elastically flexible element is parted in two sections of U-shape form as corrugated hinge strips, while an intermediate inflexible section remains. Such a hinge has its most relaxed position when the corrugated hinge strips are at least curved. This condition occurs in a position between opened and closed.